Method of coating metallic articles to prevent oxidation.



MYBON L-CEOWE, 0F HOLLISTON, MASSACHUSETTS.

mn'rnon or coarrne' ia'n'rarnrc narrows TO PREVENT oxrne'rron.

No Drawing.

To all whom it may concern:

Be it known that I, MYRONL. Crown, a

citizen of the United States, and a resident manufacture, or parts thereof, constructed of iron or steel, so as to formthereon a black or dark-colored finish or coating which is rust-resistant and which improves the appearance thereof.

My process, which accomplishes the desired purpose, consists in dipping the articles to be treated in a molten bath of caustic alkali and a nitrate of the alkali metals. Although I may use caustic potash and potassium nitrate, I preferably employ sodium hydroxid and sodium nitrate because of the excellent results secured loy their use. I employ these two substances in approximately the proportion of two parts by bulk of the nitrate to three parts of the hydrate,

but I may vary the proportions within fairly wide limits without noticeable change in the result upon the articles undergoing treatment. These two substances in dry form are thoroughly mixed, and after being placed in a suitable receptacle, are heated to a temperature of from 900 to 1200 F. They fuse at approximately 400 F. and when they reach 900 F. a scum appears which I have noted as roughly indicating that the bath is ready for use.

The articles to be. treated, such as chains, parts of typewriting or other machines, fire arms, cutlery, hardward, etc., are dipped into the molten bath for an instantsay for a period of. from 1 to 10 secondsbut usually from 3 to 5 seconds, and they are then withdrawn. Then I dip the article into a bath of water, for cooling purposes, this taking but an instant, and then I immerse it into boiling water for a short time,

say for three or four minutes, the efiect of which is to remove any of the material of the first bath which may have lodged in the crevices or corners, if there be any, in the article. Then the article is dried n sawdust or by any other approved method, and

Specification of Letters Patent. Pat gmted Nimy, 2t}, 1911?, Application filed April 3, 1915. Serial No. 19,039;

then is immersed for a few moments, say 2 or 3 mlnutes, in a bath of boiling oil of any sultable klnd. I may for example use lard oil, cotton seed oil, orother equivalent material.

AS a result of the treatment I have descr1bed, the article will have formed thereon a black'or nearly black finish, which islustrous or dull according to Whether or not the article had becn'previously polished. Iron or steel articles so treated are rust resistant, present an attractive appearance,

being black or substantially so, and, due.

to the heat of the first bath and the subsequent step, have a hardened exterior. The process is very cheap and takes very little time.

Having thus explained the nature of my said invention, and described a way of makmg and using the same, although without attempting to set forth all of the forms in which it may be made or all of the modes of its use, what Iclaim is 1. A method of imparting a black or substantially black rust-resistant finish to articles of iron or steel, which includes immersing them momentarily in a bath consisting v of a mixture of molten nitrate of the alkali I metals and caustic alkali.

2. A method of imparting a black or suhstantially black rust-resistant finish to articles of steel or iron, which includes immersing them in a bath .of molten sodium hydroxid and sodium nitrate heated to a temperature of approximately not less than 900 F.

3. A method of imparting a black or substantially black rust-resistant finish to articles of iron or steel, which consists in immersing them in a bath of sodium hydroxid and sodium nitrate heated to approximately not less than 900 F., and immersing the same in boiling water to remove the excess {)naterial left upon the articles from the first ath.

- 4. A method of imparting a black or sub- .stantially black rust resistant finish to articles of iron" or steel, which consists inimmersing them in a bath of sodium hydroxid and sodium nitrate heated to approximately not less than 900 F., immersing the samestantia-Hy black rust-resistant finish 11:0 artidies of iron or steel, which consists in immersing them in a bath of sodium hydroxid and sodium nitrate heated to approximately not less than 900 F, immersmg the same in boiling water, coolin the same by immersion 1n Wmer, removlng the excess material left from the first bath by immersing;

neemoee them in boilingwater, drying said. articles,

and immersing them in boiling oil.

In testimony whereof I have afiixed my signature, in presence oftwo Witnesses.

v MYRON L. CRDWE.

Witnesses: Gnome CHANDLER Com,

CHESTER A. REED. 

